The present invention relates to spark gap devices and particularly to spark gap devices for providing additional protection to existing equipment.
Communication equipment such as a telephone subscriber station is conventionally provided with a spark gap protector for shunting hazardous overvoltage surges to ground. These overvoltage surges can be caused by lightning strokes, power contact of the communication lines with voltage supply lines, power induction, ground potential rise and static buildup. The spark gap device is usually in the form of a station protector which may include carbon block electrodes, and a means for permanently shorting the protector after an extended discharge. While the device is generally effective in the case of overvoltages and excessive currents, the breakdown voltage is not always readily predictable. Moreover, the carbon block electrodes are replaceable and in a given instance may not have been properly replaced, resulting in the loss of electrical protection that is not readily observable from the exterior of the device. Furthermore, carbon dusting and consequently noisy circuits can result from the operation of carbon block gaps. Present add-on devices are the type that fuse open, lift off, and require the carbon blocks as back up protection.